Invasive grass fuels increased fire activity in the West

An invasive grass species may be one reason fires are bigger and more frequent in certain regions of the western United States, according to a team of researchers.

Share:

Total shares:

FULL STORY

Cheatgrass (yellow) in the foreground, dominate only about 6 percent of the Great Basin, but the average fire size is larger than in other ecosystems dominated by sage or pinyon, for example.

Credit: Mike Pellant, Bureau of Land Management

Cheatgrass (yellow) in the foreground, dominate only about 6 percent of the Great Basin, but the average fire size is larger than in other ecosystems dominated by sage or pinyon, for example.

Credit: Mike Pellant, Bureau of Land Management

An invasive grass species may be one reason fires are bigger and more frequent in certain regions of the western United States, according to a team of researchers.

Researchers used satellite imagery to identify cheatgrass, a plant species accidentally introduced by settlers in the West during the 1800s, in a disproportionately high number of fires in the Great Basin, a 600,000 square-kilometer arid area in the West that includes large sections of Nevada, as well as parts of Utah, Colorado, Idaho, California and Oregon.

"Over the past decade, cheatgrass fueled the majority of the largest fires, influencing 39 of the largest 50 fires," said Jennifer Balch, assistant professor, Penn State's Department of Geography and Earth and Environmental Systems Institute. "That's much higher than what it should be when you consider how much of the Great Basin that cheatgrass covers."

The average size of the fires in cheatgrass grasslands, which dominate only about 6 percent of the Great Basin, was significantly larger than the average fire in most regions dominated by other vegetation, including pinyon-juniper areas, montane shrubland and agricultural land.

In addition to targeting the influence of cheatgass on major fires, the researchers, who reported their findings in the online version of Global Change Biology, also found that the plant may play a role in increasing the frequency of fires, said Balch.

"From 2000 to 2009, cheatgrass burned twice as much as any other vegetation," said Balch.

One of the consequences of more widespread cheatgrass fires is that landscapes dominated by the grass have a shorter fire-return interval -- the time between fires in a region -- of 78 years, compared to other species like sagebrush, which has a 196-year fire return interval.

"What's happening is that cheatgrass is creating a novel grass-fire cycle that makes future fires more likely," said Balch, who started this work at the National Center for Ecological Analysis and Synthesis. "Fire promotes cheatgrass and cheatgrass promotes fires."

The ability of cheatgrass to rapidly spread and fill in the ground between other plant species may be one reason the plant is involved in larger and more frequent blazes, said Balch, who worked with Bethany Bradley, assistant professor of environmental conservation, University of Massachusetts-Amherst; Carla D'Antonio, professor of ecology, evolution and marine biology, University of California-Santa Barbara, and José Gómez-Dans, research associate in the department of geography and the National Centre for Earth Observation, University College London.

Balch said the cheatgrass-influenced fires create a difficult management challenge. The fires can threaten agricultural lands and, since more people are building homes in the west, residential areas as well as habitat for threatened native wildlife, such as the greater sage grouse.

While cheatgrass-driven fires have been recognized for decades, remote sensing technology has allowed the researchers to take a regional approach to assessing the problem. They compared burned area detected by NASA's Moderate Resolution Imaging Spectoradiometer between 2000 to 2009 to regional land cover maps that included cover of cheatgrass.

"Historically, the way remote sensing worked, you could only tell the difference between broad land cover classes such as trees versus wetlands, for instance," Bradley said. "It is very difficult to capture those details at the species level."

However, by noticing what conditions favor the growth of certain species, the researchers were able to use the satellite imagery to better pinpoint the growth of different species. For instance, cheatgrass grows during wet periods while many other species do not, Bradley said.

"What you end up seeing is that most years when it is dry, the cheatgrass doesn't grow much," said Bradley. "But when there are wet seasons that occur due to the El Nino cycle, cheatgrass cover is very dense and continuous."

Bradley added that this is a concern because cheatgrass now dominates more than 40,000 square kilometers, an area that is more than 100 times the size of Salt Lake City, Utah.

According to the researchers, those changes in the vegetation can be detected in the satellite images.

"Being able to detect cheatgrass and burns really enabled us to ask the important question: 'How does an invasive plant change fire activity across the entire Great Basin?'" Balch said.

The National Science Foundation and the National Center for Ecological Analysis and Synthesis supported this work.

Story Source:

The above post is reprinted from materials provided by Penn State. Note: Materials may be edited for content and length.

July 31, 2015  Resettlement projects in the Amazon are driving severe tropical deforestation, according to new research. Widely hailed as a socially responsible and 'innocuous' strategy of land redistribution, ... read more

July 31, 2015  The humble butterfly could hold the key to unlocking new techniques to make solar energy cheaper and more efficient, pioneering new research has shown. By mimicking the v-shaped posture adopted by ... read more

July 30, 2015  China needs to reduce its dependence on coal and improve the range of fuels it uses if it is to have long term energy security, according to new research. The study looks at the future of electricity ... read more

July 30, 2015  North of the Aleutian Islands, submarine canyons in the cold waters of the eastern Bering Sea contain a highly productive 'green belt' that is home to deep-water corals as ... read more

July 30, 2015  New findings have implications for questions regarding how animals and plants grow minerals into shapes that have no relation to their original crystal symmetry, and why some ... read more

July 30, 2015  A new study addresses an important question in climate science: how accurate are climate model projections? Climate models are used to estimate future global warming, and their accuracy can be ... read more

July 21, 2015  Controlled burning is widely used to maintain biodiversity and enhance regeneration of important deciduous tree species such as oak and hickory, but a recent study found that this practice also ... read more

Apr. 23, 2014  The uncontrolled method of managing agricultural areas each year turns the entire southern tip of Primorsky Province into an enormous firebed, enveloping up to 40 percent of the entire ... read more

Aug. 12, 2013  Researchers have identified gamba grass and other invasive weeds as a potential threat to landholder involvement in environmental offset programs such as the Carbon Farming Initiative. Strategic ... read more

Aug. 27, 2010  Controlling juniper trees by cutting them down and burning them where they fall keeps invasive cheatgrass at bay and allows native perennials to become re-established, according to new ... read more